1. Field of the Invention
The present invention relates to an ATM adaption layer (AAL) switch in a mobile communication system, and more particularly to a switching method and an AAL2 type AAL switch for multicast.
2. Background of the Related Art
An AAL2 switch is one of the core technologies of IMT-2000, which combines ATM signals for efficient use of broadband width in an ATM network that is used as a transmission path between stations using IMT-2000, i.e., a base station, base station controller and mobile switching center. FIG. 1 is a block diagram of a related art ATM switch system.
Referring to FIG. 1, the related art ATM switch system includes an AAL2 receiving end 11, an ATM switch 12, and an AAL2 transmitting end 13. An AAL2 packet is demultiplexed by the AAL2 receiving end 11, and the AAL2 packet is converted into an ATM cell of 53 bytes having an internal format. The converted ATM cell, i.e., the common part sublayer packet (CPS) is switched by the ATM switch 12, and reverse-converted into the AAL2 CPS packet from the internal format, and multiplexed by the AAL2 transmitting end 13 to be transmitted to a destination.
As described above, the ATM switch 12 does not switch the AAL2 packet immediately or directly, but first has to convert the AAL2 packet into an ATM cell using the internal format. Further, when performing the switching at an ATM level, the related art ATM switching system cannot achieve the AAL2 multicast switching due to the CPS packet in a multiplexed state.
As described above, the related art ATM switch system has various disadvantages. As shown in FIG. 1, in the related art ATM switching system, the AAL2 packet has to be converted into CPS packet by the internal format. After the switching, the converted CPS packet has then to be re-converted into AAL2 CPS packet. Such an overhead causes service quality deterioration and efficiency deterioration such as delayed transmission of cells. Further, many manufacturers develop proprietary or use their own internal formats such as AAL2 and AAL5. Further, since the related ATM switch system cannot support the multicast function of multiplexed AAL2, it is impossible to apply the system to the 3-G mobile communication system like the IMT-2000. In the related art ATM switch system, since the ATM cell multiplexed into AAL2 packet has a plurality of user information, the AAL2 packet has to be divided into CPS packets to be copied into a plurality of cells. Accordingly, there have been increasing demands and a need exists for an AAL2 switch for multicast, which will achieve a more efficient communication system and increase or maximize the traffic transmission efficiency.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.